What is a GMT Watch and How to Use One?
What is a GMT Watch?
GMT stands for Greenwich Mean Time and is point “0” on the 24-hour international timezone scale. To put it simply, a GMT watch is a timepiece that displays both a 24-hour and a 12-hour timescale. To find out what they look like, then check out our collection of luxury Fileteado GMT watches at Franck Dubarry. A GMT watch has developed into a timeless and fashionable device over recent years, but not many people know about its fascinating history.
A Brief History
In the Beginning, There Was Latitude
It all started during the age of ship exploration. Humans began to travel long distances overseas and it became important to track their progress on maps. Remember those horizontal lines across the globe in your geography class? Those are known as lines of latitude, which are distributed around the Earth using the equator as the origin. Ship crews measured this using a sextant: a device that calculated the angle of the stars to the horizon. However, knowing only the latitude didn’t help to plot ships on the map. Vertical lines (longitude) were also required and that’s where GMT comes in.
Then There Was GMT
Without an obvious origin, it was eventually decided that the 0-degree vertical line should run through the Royal Observatory in Greenwich, London. This line was called the Prime Meridian and noon is declared when the sun reaches its highest point directly above it. However, the Earth’s elliptical orbit and tilted axis complicate things a little and the real 12pm GMT is usually a few minutes out of sync each day. Fortunately, an annual average was calculated to solve this discrepancy, making GMT the average solar time, unaffected by Daylight Savings. Now that there were timepieces displaying GMT, it was possible to determine the longitude by observing the position of the sun at noon and calculating the difference between local and GMT time. So GMT watches are perfect for boat travel...but how is that relevant to you?
The Age of Plane Travel
Then there was plane travel. Suddenly, humans were zooming across multiple timezones incredibly quickly. In order to help their staff to keep track of time, Pan Am Airlines approached Rolex and asked for a new watch design. In 1954, the GMT watch was born. In short, the GMT watch was designed to display both the GMT and one other timezone. However, the ingenious design of the watch enabled its owners to use it for other functions as well. For this reason, GMT watches quickly gained popularity and, soon after their first release, all sorts of people were wearing them, not just pilots.
For business people keeping in touch with their foreign clients, to medical professionals attending conferences abroad, worldwide travelers and even those who choose to stay in one timezone. GMT watches are for anyone and everyone. However, some things have changed since the first days of longitude and we currently use Coordinated Universal Time (UTC). It was invented to replace GMT in 1955 and is much more accurate than other time-keeping methods. However, to avoid major confusion and disruption to timezones, no significant change was made to the GMT scale and so the term GMT is still commonly used.
GMT Watch Movement: How Does it Work?
The pure brilliance of a GMT watch comes from its simplistic and ingenious engineering. The 24-hour clock hands usually have a different color and are geared to turn half as quickly as the 12-hour hands. To put it simply, the 12-hour clock hands complete a full rotation twice a day. Whereas, the 24-hour clock hands spin around only once. The 24-hour watch also enables the user to easily distinguish whether it is AM or PM.
How to Set a GMT Watch?
Nowadays, GMT watches have multiple functions depending on what you need them for. Below we will outline some of the basic features and how to use them:
How to Show GMT and Local Time
The original function of the GMT watch was to show GMT time and this is easily achieved by setting the 24-hour hands to align with that. As long as you know the timezone of your current location, the 12-hour hands can then be changed according to the position of the 24-hour hands. For example, if you are in Germany, then the timezone is GMT +1. If the GMT time states 9am, then you would simply turn the 12-hour clock’s hour hand to 10 and the minute hand to 0.
How to Distinguish Between AM or PM
Some people may not be concerned about what time it is in Greenwich and therefore, the 24-hour clock can also be set to your current timezone. This way, you will always be able to quickly distinguish whether it is the morning or the afternoon: a feature that is lacking on the traditional analog watch.
How to Display Multiple Timezones
Some GMT watches come with a rotating bezel, which is a ring feature around the clock face of the watch. This often has markings to show timezones of different cities, which means that you can tell the time in multiple locations simply by turning the bezel.